Research and Design of Hydro-mechanical Continuously Variable Transmission for Tractors

A new type continuous variable transmission device, a hydro-mechanical continuously variable transmission （HMCVT） for agricultural tractors is developed, which is composed of a single planetary gear differential train, a hydraulic transmission system consisted of variable displacement pump and fixed displacement motor and a multi-gear fixed step radio transmission. Based on the analysis of types of hydrostatic mechanical transmission （HMT） and styles of hydraulic transmission, the general drive scheme for HMCVT is obtained. The method of selecting mechanical parameters and hydraulic units is explained, and the stepless speed regulation characteristic of HMCVT is analyzed. This paper also specializes the calculating method of transmission efficiency. It shows that tractors assembled with HMCVT can obtain a continuously variable speed and achieve high drive efficiency.

ZHONGCE Tractors & Automobiles Co. Ltd

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Prediction of Repair and Maintenance Costs of Two-wheel Drive Tractors in Iran

Predicting of repair and maintenance （R＆M） costs of tractors in any mechanized farm is necessary for owners and managers to obtain information on overall costs and to control financial balance and production economy. In this context a study was conducted to predict accumulated R＆M costs （Y） of two-wheel drive （2WD） tractors based on accumulated usage hours （X） in Misagh-e-Sabz Agribusiness Company in Iran. Recorded data of the company were used to determine regression models for predicting accumulated R＆M costs （as percentage of initial purchase price） based on accumulated usage hours. The statistical results of the study indicated that in order to predict accumulated R＆M costs of 2WD tractors with accumulated usage hours of 2260 h or less the power regression model Y=0.013 （X/100）1.677 with R2=0.976, and to predict accumulated R＆M costs of 2WD tractors with accumulated usage hours of 2260 h or more the polynomial regression model Y=0.004 （X/100）2-0.181 （X/1 00）＋4.373 with R2=0.998 can be strongly suggested.

Double tractors swing microendoscopic discectomy technique for multi-segmental lumbar disc herniation

Objective To evaluate the effect of double tractors swing microendoscopic discectomy technique in multisegmental lumbar disc herniation.Methods From December 2006 to November 2009,153 patients with multisegmental lumbar disc herniation

Comparison of Economic Life of Tractors in Iran Using Condition Monitoring （CM） and Breakdown Maintenance （BM） Methods

Repair and maintenance costs are the most important factors affecting decision making about substituting agricultural machineries. This decision is made based on the economic life （time） of machineries. In this research, condition monitoring of MF285 and MF399 tractors was performed using engine oil analysis to find the optimum life time of tractor substitution in comparison with the breakdown maintenance method in Iran. All recorded information about fixed and variable costs were selected as data base and analyzed. Data were divided （classified） based on period of annual working time. Using power regression analysis led to find mathematical models for the optimum time life definition. Cumulative working time （X） was selected as independent and cumulative costs based on definite percent of initial price （Y） was considered as dependent variable and a power law equation was found to express the costs of both MF399 and MF285 tractors as a function of working time. Results showed that in CM method, average of economic life was 13 and 11 years for MF399 and MF285, respectively. It was also found that in BM method, economic life wasl0 and 8.5 years for MF399 and MF285, respectively.

Evaluation of Environmental Impacts in the Wood Skidding with Tractors in Greece

The contemporary demands of the forestry exploitation for quantitative and qualitative increase of timber production are directly related with the mechanization of the wood skidding works. In Greece, the suitable machinery for wood skidding are those with low amortization, operation and installation expenses, are flexible, and may also be used for other farming works （since they are not used very often for wood skidding） and cause the smaller damages to the wood, the forest, the soil and the environment in general. In this paper, it studies the environmental impacts in the remaining stand as much as during the pre-skidding as well as during the main wood skidding with tractor in the forest of Arnaia, Prefecture of Halkidiki, in order to draw out useful conclusions for the improvement of the machinery application methods and the protection of the environment.

Review of electro-hydraulic hitch system control method of automated tractors

The automatic and intelligent degree of tractor hitch system determines the operations quality,efficiency,tractor power output and energy consumption,and automatic control of electro-hydraulic hitch is one of the key technical problems in the realization of automated tractor.In this study,the adjustment methods and characteristics of electro-hydraulic hitch system were summarized.The development of electro-hydraulic hitch control technologies was elaborated and analyzed from both the electro-hydraulic control strategy and slip control strategy perspectives.The implementation methods and control characteristics were discussed.A new idea for the development of automated tractor was put forward that integrating cutting-edge technologies such as big data,fusion control and artificial intelligence.In addition,based on the precise and efficient control of electro-hydraulic hitch system,a high reliability of the control system of the tractor with intelligent application of the control algorithm was obtained.The results can provide a reference for the precise operation of automated tractors under the big data in agriculture.

Design and optimization of a new terrain-adaptive hitch mechanism for hilly tractors

In view of the problems of poor working quality and low efficiency caused by traditional hitch mechanisms,which cannot make farm implements adapt to hillside fields for terrain-adaptive working after leveling the body of hilly tractors,a new type of terrain-adaptive hitch mechanism was designed which can adjust the transverse posture of farm implements to meet the ploughing requirements of complicated terrain in hilly and mountainous areas.The mechanism was mainly composed of the original hitch device and the newly added rotating device.The kinematic model of each sub-mechanism was established,as well as the mathematical relation of significant performance indexes of the whole mechanism,such as lifting capacity,transverse inclination angle and tillage depth.Genetic algorithm was used to optimize the lifting performance of this hitch mechanism in Matlab,so that the minimum vertical lifting force at the center of gravity of farm implements increased by 14.1%,which met the requirements of national standards.Through ADAMS simulation calculation,it was found that different working slopes had a certain influence on the external load of each component,and terrain-adaptive hitch mechanism had little effect on the vibration characteristics of hilly tractors.The fatigue analysis and optimization design of the key component,rotating shaft,were carried out in ANSYS Workbench,and the mass of this part reduced by 64%.A real vehicle test platform was set up to test and verify the power lifting range and working slope range of terrain-adaptive hitch mechanism.The test results showed that the actual power lifting ranged in 185-857 mm,and the maximum error from the theoretical range was only 3.1%,while the actual working slope range was from–25.9°to+23.2°,and the maximum error from the theoretical range was only 4.5%.Therefore,the terrain-adaptive hitch mechanism can meet the requirements of power lifting performance,and simultaneously can adjust the transverse posture of farm implements for adapting to hillside fields of no less than 20°.

Control algorithm and energy management strategy for extended range electric tractors

It is difficult to make full use of the electrical energy of the power battery for extended-range electric tractors because the battery’s state of charge may be relatively high at the end of the running mileage.To address this situation,this paper aimed to study the control parameter adjustment in relation to the power battery’s electrical consumption and the diesel engine’s fuel consumption energy management strategy.Based on the AVL-Cruise simulation platform,the vehicle model of the tractor was established,and the control module of AVL-Cruise was used to compile the energy management strategy.In order to verify the superiority of the proposed strategy,the contrast strategy was employed in terms of the diesel engine start and stop control plus fixed point energy management strategy(FPEMS).The applicability of the proposed strategy was tested through continuous transfer operation and the small area deep loosening operation.The simulation results show that the proposed strategy was of good applicability.Compared with the FPEMS,the fuel consumption reduced significantly,and the electrical consumption of the power battery increased obviously.

Fuel economy of multiple conditions self-adaptive tractors with hydro-mechanical CVT

Fuel economy is one of the most important properties of wheeled tractors.To improve the fuel economy,it is necessary to improve the engine fuel economy and the tractive efficiency of the driving mechanism.By analyzing the fuel economy evaluation index of wheeled tractors,the correlation among the tractor specific fuel consumption,the engine effective specific fuel consumption and the tractive efficiency of the driving mechanism were clarified in this paper.A tractor with a new type of hydro-mechanical continuously variable transmission(HMCVT)was designed and its whole model was established too.On the basis of each module’s simulation model,the binary speed ratio matching simulation model of the gearbox-engine system was obtained by the control system reconstruction,and the fuel economy simulation analysis of the wheeled tractor with HMCVT was carried out under the two typical working conditions of plowing and sowing.Compared with the current national standard,the fuel economy of the newly designed wheeled tractors with the power of 130 kW was 380 g/(kW·h),specific fuel consumption was reduced by 21.1%.The results showed that the new tractor fuel economy was greatly improved.Further,automatic navigation technology can be combined with the self-adaptive tractors to adapt to different working conditions and achieve the optimal fuel economy,which can be applied in precision agriculture.

Ergonomic assessment of drivers in MF285 and MF399 tractors during clutching using algometer

Tractor as one of the most widely used agricultural machinery should be considered from different aspects.The frequent application of clutch and brake pedals and also the steering wheel within farms,along with the unfavorable working conditions,cause negative effects on the occupational health of the tractor drivers.Thus,in this research,the imposed forces on three engaged muscles including:Gastrocnemius,Trapezius and Quadrate’s lumborum of the tractor drivers during clutching have been studied.In this regard,algometer device was used to determine the applied forces on selective muscles of drivers during clutching of MF285 and MF399 tractors.The experiments were performed employing sample of 30 drivers and were conducted on two Iranian frequently used tractors including:MF285 and MF399 models.The results showed that the clutching forces for MF285 and MF399 tractors were 340 N and 290 N,respectively.The knee angle of the drivers of the two tractors was statistically different at the one percent level of significance.The reduction of pain threshold after 30 and 60 s clutching and also 60 s rest after clutching in MF285 tractor,for all three muscles,were more than those of MF399 tractor.The impact of clutching on the average decreases of pain threshold,for all drivers and all clutching periods,during and after clutching,in the Quadratus lumborum muscle was more than the other two muscles,in both tractors.In order to reduce the clutching force for MF285 tractor some modifications is suggested.In this regard the force transfer joint between the pedal and the clutch release linkage may be replaced with one made of cast iron.

Comprehensive lumped parameter and multibody approach for the dynamic simulation of agricultural tractors with tyre–soil interaction

Modern agricultural tractors are complex systems,in which multiple physical(and technological)domains interact to reach a wide set of competing goals,including work operational performance and energy efficiency.This complexity translates to the dynamic,multi‐domain simulation models implemented to serve as digital twins,for rapid prototyping and effective pre‐tuning,prior to bench and on‐field testing.Consequently,a suitable simulation framework should have the capability to focus both on the vehicle as a whole and on individual subsystems.For each of the latter,multiple options should be available,with different levels of detail,to properly address the relevant phenomena,depending on the specific focus,for an optimal balance between accuracy and computation time.The methodology proposed here by the authors is based on the lumped parameter approach and integrates the models for the following subsystems in a modular context:internal combustion engine,hydromechanical transmission,vehicle body,and tyre–soil interaction.The model is completed by a load cycle module that generates stimulus time histories to reproduce the work load under real operating conditions.Traction capability is affected by vertical load on the wheels,which is even more relevant if the vehicle is travelling on an uncompacted soil and subject to a variable drawbar pull force as it is when ploughing.The vertical load is,in turn,heavily affected by vehicle dynamics,which can be accurately modelled via a full multibody implementation.The presented lumped parameter model is intended as a powerful simulation tool to evaluate tractor performance,both in terms of fuel consumption and traction dynamics,by considering the cascade phenomena from the wheel–ground interaction to the engine,passing through the dynamics of vehicle bodies and their mass transfer.Its capabilities and numerical results are presented for the simulation of a realistic ploughing operation.

Reducing Operation Emissions and Improving Work Efficiency Using a Pure Electric Wheel Drive Tractor

In response to the problems of excessive greenhouse-gas and particulate emissions and the low traction efficiency of conventional diesel tractors in the field,a purely electric wheel-side drive tractor was studied,including an electric motor drive system,a battery ballast system,and an electro–hydraulic suspension system.This paper develops a dynamics model of an electric tractor-ploughing unit under complex soil conditions,leading to the proposal of an active control method for drive wheel torque and a joint control method for the traction force of the suspension system and the front-and rear-axle loads of a tractor.Finally,the tractor is prototyped and assembled,and ploughing tests are carried out.The ploughing results show that the active torque-distribution control method proposed in this study reduces the tractor slip by 14.83%and increases the traction efficiency by 10.28%compared with the average torquedistribution mode.Compared with the conventional traction control mode,the joint control method for traction and ballast proposed in this paper results in a 3.7%increase in traction efficiency,a 15.05%decrease in slip,and a 4.9%reduction in total drive motor energy consumption.This study will help to improve the operation quality and traction efficiency of electric tractors in complex soil conditions.

Design a Special Fixture for Tractor Lever

Aiming at the problems of long time and poor machining precision in processing the tractor lever workpiece,a special fixture suitable for the tractor lever workpiece is designed by analyzing the processing technology of the lever workpiece,and the workpiece is accurately positioned and tightened under the action of the special fixture.Efficient machining of the workpiece can be achieved by using a drill template.The fixture not only has the advantages of high production efficiency,low cost and high life,but also effectively improves the processing technology of the workpiece,and has certain reference value for the subsequent fixture improvement design.

Path tracking control of autonomous agricultural mobile robots

In a tractor automatic navigation system, path planning plays a significant role in improving operation efficiency. This study aims to create a suboptimal reference course for headland turning of a robot tractor and design a path-tracking controller to guide the robot tractor along the reference course. A time-minimum suboptimal control method was used to generate the reference turning course based on the mechanical parameters of the test tractor. A path-tracking controller consisting of both feedforward and feedback component elements was also proposed. The feedforward component was directly determined by the desired steering angle of the current navigation point on the reference course, whereas the feedback component was derived from the designed optimal controller. Computer simulation and field tests were performed to validate the path-tracking performance. Field test results indicated that the robot tractor followed the reference courses precisely on flat meadow, with average and standard lateral devia- tions being 0.031 m and 0.086 m, respectively. However, the tracking error increased while operating on sloping meadow due to the employed vehicle kinematic model.

Multi-objective Stability Control Algorithm of Heavy Tractor Semi-trailer Based on Differential Braking

Rollover and jack-knifing of tractor semi-trailer are serious threats for vehicle safety, and accordingly active safety technologies have been widely used to reduce or prevent the occurrence of such accidents. However, currently tractor semi-trailer stability control is generally only a single hazardous condition (rollover or jack-knifing) control, it is difficult to ensure the vehicle comprehensive stability of various dangerous conditions. The main objective of this study is to introduce a multi-objective stability control algorithm which can improve the vehicle stability of a tractor semi-trailer by using differential braking. A vehicle controller is designed to minimize the likelihood of rollover and jack-knifing. First a linear vehicle model of tractor semi-trailer is constructed. Then an optimal yaw control for tractor using differential braking is applied to minimize the yaw rate and lateral acceleration deviation of tractor, as well as the hitch articulation angle of tractor semi-trailer, so as to improve the vehicle stability. Second a braking scheme and variable structure control with sliding mode control are introduced in order to achieve the best braking effect. Last Fishhook maneuver is introduced to the active safety simulation and the active control system effect verification. The simulation results show that multi-objective stability control algorithm of semi-trailer could improve the vehicle stability significantly during the transient maneuvers. The proposed multi-objective stability control algorithm is effective to prevent the vehicle rollover and jackknifing.

Path-tracking Control of a Tractor-aircraft System

An aircraft tractor plays a significant role as a kind of important marine transport and support equipment. It＇s necessary to study its controlling and manoeuvring stability to improve operation efficiency. A virtual prototyping model of the tractor-aircraft system based on Lagrange＇s equation of the first kind with Lagrange mutipliers was established in this paper, According to the towing characteristics, a path-tracking controller using fuzzy logic theory was designed. Direction control herein was carried out through a compensatory tracking approach. Interactive co-simulation was performed to validate the path-tracking behavior in closed-loop, Simulation results indicated that the tractor followed the reference courses precisely on a flat ground.

Design of User Interface for Tractor Cab Real-time Information Management System

In this paper,the user interface of tractor cab real-time information management system was designed. Based on the principle of "user friendly",it reasonably arranged spatial position of information management system according to spatial distribution of tractor cab. Then,it analyzed operation habits and thinking ways of drivers,and formulated design principle meeting demands of drivers. Besides,it used LabView software to design user interface,including interface layout and interface design. User interface includes basic information interface,job information interface,camera monitoring interface,and fault diagnosis interface. Finally,it made evaluation of the user interface from color,indicator lamp,dial,and pointer. Results indicate that the designed user interface layout conforms to cognition mentality and operation habits and easy to get familiar and grasp; graphical interface is vivid and easy to stimulate pleasure of drivers in operation; interface color matching is coordinated; the layout of controls is hierarchical and logic,and operating mode is consistent with Windows system.

A Newly Developed Differential Steering Rubber-tracked Agriculture Tractor

This paper introduces a newly developed ag tractor.The differential steering system and rubber tracks are described in detail.

Design and Experiment of Electronic-hydraulic Loading Test-bed Based on Tractor's Hydraulic Steering By-wire

An Electro-hydraulic loading system is designed based on a test-bed of tractor's hydraulic steering by-wire. To simulate the steering resistance driving tractor in many kinds of soils and roads,the loading force is controlled to make proportional and continuous variable by an electro-hydraulic proportional relief valve. A steering resistance loading test-bed is built to test three kinds of steering resistance including constant,step and sine style. Tire lateral resistance is also tested under different steering conditions. The result shows that the electro-hydraulic loading system has high stability and following performance. Besides,the system's steady state error is lower than 3. 1%,and it meets the test requirement of tractor's hydraulic steering by-wire.